My go-to casual look when I'm feeling vintage is a Bettie Page black v-neck t-shirt, dark-wash skinny jeans, and leopard-print flats from Target. For makeup, I love MAC Frankly Scarlet blush and my usual thick, winged, black liquid liner. I still haven't found my perfect casual hairdo, so I just part it on the side a la Veronica Lake.
Do you have a Francesca's or Charming Charlie store near you? Both of these stores carry fantastic, inexpensive jewelry, shoes, and clothing, and many of their items are slightly vintage-inspired.